1. Field of the Invention
The present invention relates to filters, and in particular, to a high pressure liquid filter vessel which provides for easy replacement of the associated filter bag, without contaminating the fluid remaining in the housing.
2. Description of the Relevant Art
Many different filters are in use today in industry. A major concern with the industrial type filter is the ease in which the filter elements can be replaced, since it requires shut-down of the production facility in order to provide this type of maintenance. Many elaborate arrangements are utilized to make the time consuming job of changing filters acceptable. One approach for simplifying this task is disclosed in U.S. Pat. No. 3,640,392 issued to E. A. Smith, et al. on Feb. 8, 1972. The Smith, et al. disclosure overcame the problems known in the prior art, by eliminating the need for disconnecting couplings, flexible hoses, or other types of mechanisms for manually disconnecting the liquid inlet line, in order to open the top of the filter vessel. The apparatus disclosed therein provides for a permanent plumbing connection for the pressurized liquid being filtered and does not interfere with the easy opening of the vessel for inspection, replacement of the filter bag and cleaning. The vessel is provided with a cover connected by a unique hinge, contains a basket supported filter bag for filtering the liquid under pressure that enters the mouth of the bag through an inlet in the cover and is discharged through an outlet in the bottom of the vessel. The hinge is provided with a liquid inlet passage which communicates with a liquid supply plumbing connection that is permanently affixed and need not be disturbed when the cover is opened or closed. An annular seal is provided by the rim of the filter basket disposed on the annular wall of the body of the vessel so that when the cover is closed and clamped, leakage of the pressurized liquid is prevented above the bag, as well as from the vessel itself. The plumbing required to provide for a pressurized liquid into the cover arrangement as disclosed, requires a movable plumbing joint which has a tendency to wear with time, and thereby, permits the pressurized fluid to leak out of the connection. The filter basket requires a unique configuration and utilizes a pair of O-rings to provide the liquid seal in order to prevent leakage between the cover and the vessel housing.
Other techniques have been utilized to maintain a filter in fixed relation between a pair of members such as a cover and a housing. Typical of these is U.S. Pat. No. 2,727,634 issued on Dec. 20, 1955 to J. P. O'Meara which discloses upper and lower housing elements having a rubber O-ring and filter disposed therebetween. The housings are held together by a U-shaped bracket arrangement or strap which is wrapped around the assembly and tightened down. However, this arrangement requires that the housing be rigid, therefore, metallic, and does not insure equal pressures being applied completely around the circumference, since the strap exerts pressure on half-circle bands having spaces therebetween.
Another embodiment is disclosed in U.S. Pat. No. 3,147,220 issued to T. P. Avery on Sept. 1, 1964, wherein a U-shaped band assembly, utilizing four hingeable segments, sandwiches a cover flange and a housing flange with a gasket therebetween in order to provide a pressurized seal. Hereagain, the filter housing and clamp must be made of metal and with a segmented bracket assembly as disclosed the pressure is only equalized because the elements are all non-resilient metal.
Another filter arrangement is disclosed in U.S. Pat. No. 3,931,015 issued to B. M. Jenkins on Jan. 6, 1976 wherein the cover of the filter vessel is held to the housing by a U-shaped flexible clamp applying pressure to a flange provided on the cover and housing, which sandwich a rubber or resilient gasket therebetween. Here again, in order to maintain a high pressure arrangement the cover and housing were required to be made of metal, which is not suitable for the filtering of corrosive liquids.
A further attempt to overcome the shortcomings heretofore mentioned is disclosed in U.S. Pat. No. 4,253,959 issued to P. T. Tafara on Mar. 3, 1981. The disclosure therein utilizes a non-metallic cover and housing which provides a seal by threadedly engaging the cover to the housing with an O-ring disposed along the vertical housing wall above the threaded portion that comes into intimate contact with the inner wall of the cover as the cover is threaded thereon. This type of arrangement, although adequate for low pressure applications, is not suitable for high pressure use because of the difficulty in maintaining tolerances in production.